Adopted
by Proudy1019
Summary: Percy Jackson thought that his life couldn't be any weirder. From being a demigod, he had been in very weird situations before. But when his parents got killed by a fire, and then he got adopted. He thought it wasn't really THAT weird until until he saw that it wasn't a mortal that was signing the adoption papers. Instead, she was a goat. A freaking goat. How would Percy cope to li
1. chapter 1

CHARActers don't belong to me. Percy Jackson and Heroes of Olympus belong to Rick Riordan. Undertale belongs to Toby Fox. I own only my OCs and the plot.

"Mom I'm home!" A raven haired boy with sea green eyes, commonly known as Percy Jackson shouted while grabbing the doorknob and opening the door to his apartment. Percy then headed to the kitchen, where his mom normally was, making blue food for him. He smelled something burning, but he didn't think much about it. It was probably the cookies being forgotten in the stove again. He stepped into the kitchen and he was shocked. The burned corpses of his mom and his stepfather Paul were lying on the floor of the kitchen, the stove still alight with fire. He was just going tell his mom he was alright and didn't get killed after 8 months of disappearing. He went out to the living room, scrambled around and found his mom's phone. He choked in a sob as he dialed the police's number and informed them that his parents had been killed from a fire. About 10 minutes later, the police arrived and they questioned him with questions like:

"What are their relationships with you?"

"Do you have any known relatives?"

"When did you discover their corpses?"

"Where were you before coming home?"

Most of these questions were just too painful to answer. Since he didn't have mortal relatives he knew of, he would probably have to go to an orphanage. After the police left, he went to the bathroom with a flashlight in his hands, and made a rainbow. He then pulled out a golden drachma, currency of the gods and threw it into the rainbow.

"O Fleecy, do me a solid, and show me Annabeth Chase, at Camp Half Blood."

The rainbow shimmered and changed into a beautiful blonde girl with gray eyes, who was reading a book of architecture in Greek, Annabeth.

"Seaweed Brain, what happened?" Annabeth asked with a playful grin.

Percy shook his head. "My mom and Paul got killed by a fire," He looked down darkly, "but I highly suspect it isn't an 'accident' like the police said."

Annabeth's grin quickly disappeared. "Then who are you going to live with?"

"Probably in an orphanage until someone adopts me." Percy replied.

Annabeth looked at him and said, "Remember, you always will have a place in Camp. You can come and be a year round camper if you want, Percy."

"No, I don't want to be a burden to them and to Chiron." Percy said.

"Percy-" Annabeth started to say but it was already too late. Percy had already wiped out the connection with his hand.

"Ma'am, we have found a seventeen year old orphan. Would you accept him?" The police officer asked, with Percy beside him.

"Of course sir," The owner of Well Orphanage, Mrs. Ash said, "we accept kids and teens from the age 1-18!"

"Okay then,"The officer said, pushing Percy forward. "this kid is with you now, then."

Later, the officer went away and left Mrs. Ash and him alone.

"You would probably be sharing a room with Jonathan.. What's your name again, kiddo?" Mrs. Ash asked.

"Percy Jackson." Percy replied.

They reached a small room, opened the door, and found a little brown haired boy about nine years old sitting on the floor.

"Jonathan!" The little boy, Jonathan looked at her with a smile on his face when he heard his name,"This young man," Mrs. Ash began, gesturing her hand to Percy, "will be your roommate until either you or him gets adopted." Then she left the room, leaving him with Jonathan.

"Hi! I'm Jonathan as you already know, and you can call me Jon too! What's your name?" Jonathan said rapidly without catching his breath.

"My name is Percy. Nice to meet you, Jon."

Jon smiled. "I have a feeling we're going to be good friends."


	2. 2

Sorry, I know that I was not active like, forever, but I thought of this story so I decided to update again. Next week is guaranteed to have a next chapter. I've been busy with homework lately so I did not have very much time.

Disclaimer : I don't own Percy Jackson or Undertale.

After adopting Frisk, Toriel had the idea that if Frisk had a sibling it would be great. So that the poor child would have a sibling and friend to confide in. So she went to this 'orphanage' place to adopt a child. Preferably not too young and not too old. She went to the counter and asked to adopt a child. The owner was a genuinely nice person, and she seemed to like the children here very much. When she was chatting with the owner, Mrs. Ash, a dark haired boy burst into the room.

"Mrs. Ash, sorry if I'm interrupting anything, but I forgot where they ate-" He noticed Toriel, and his eyes widened. "Wait. Is. That. A.

GOAT??" He yelled, possibly surprised.

Toriel was starting to get used to people screaming and yelling when they saw her or other monsters. She understood that it was because they are not used to the monsters, but this boy was being too dramatic.

"Yes, my name is Toriel. I am one of the monsters-" His face darkened and paled at the word 'monsters', "that just got freed from the underground."

"M-monsters?" His sea green eyes that always seemed to be bright and cheerful dropped to a darker green, showing that he had history with some 'Monsters' before. Toriel saw this, and felt sorry for the child. If he experienced what she thought he experienced, a person at such a young age shouldn't experience something like this.

"Don't worry, my child, we monsters are particularly harmless and not hostile." She assured the boy.

'So it isn't my kind of monsters..' Percy thought, relieved. "As I was saying, Mrs. Ash, I forgot where the cafeteria is at."

Mrs. Ash chuckled lightly, "It's on the left of this building. Good luck on finding it, kiddo."

"Thanks, Mrs. Ash. I almost thought I wasn't going to eat breakfast anymore." He then rushed to the direction she said to him about.

"So, Ms. Toriel," Mrs. Ash cleared her throat, "so can you decide on which child to adopt yet or-"

"Mrs. Ash, I've decided now."

Frisk wasn't expecting anything for this day, really, but what they expected and what was true, naturally wasn't alike. They TOTALLY didn't expect Toriel to bring a 17 year old boy back home.

Frisk's new life began on a Sunday morning, when they were sitting on an armchair in Toriel's house, reading a book, titled, 'Humans and Monsters, Volume III', with The Fallen Human sitting right next to them.

"Seriously, they said that Monsters were JEALOUS of Humans so they attacked FIRST? This is a piece of crap." Chara groaned, used to identifying every wrong thing in the book.

"Shhh.. Chara, pay some respect to the reading room and the holy armchair." Frisk pointed to the red armchair they were sitting on.

"Hey kiddo, who 'cha talking to? Maybe you're starting to get bored so you decided to talk to yourself. Tibia honest, I think you're starting to get bonkers nowadays." Sans said, walking right through Chara.

Chara rolled their crimson red eyes, sighing, "That skeleton, he can always see AND walk through me and not even notice.."

The two spent the rest of the hour goofing around and playing jokes. Chara added sarcastic comments once in a while, and Frisk pretended to think that Chara didn't exist. Sans couldn't hear them anyways, so it was fine with Sans.

Suddenly, Toriel walked into the room, walking with a 17 year old boy.

Her voice echoed into the room that they were sitting in. "Frisk, you have a new sibling!!"

An eerie silence was found in the room, before Frisk fell off the Holy Armchair, and 3 voices weaved as one as they yelled the same words, " _WHAT!!!????_ "


	3. 3

Sans knew something was wrong with that kid the first time he saw him. Raven black hair, sea green eyes, he knew that the boy was hiding something. So naturally, the first thing he did was checking his LV. His eye sockets widened as he saw this kid's LV.

His Level Of Violence was 60. Freaking SIXTY. Even when Frisk slaughtered all of the monsters in the Underground, including himself, their LOVE was only 20. He can't even imagine the fact that he killed monsters so much... Monsters are kind and loving creatures, and all they want are peace and happiness. A creature to kill them all must be lacking a heart and soul.

Sans promised to himself that he would someday, someday, reveal and uncover the truth behind this cold, heartless murderer. Someday, someday. And without anyone finding the truth before that very day. All of them had been through trauma, especially Frisk, and he doesn't want to pressure them further. He decided that he would keep this to himself. Until that day. That day.

They were like a normal family. Toriel being the warm and tender mother, Sans being the crazy-ass big brother, Papyrus being the innocent brother, Frisk, the sassy and playful peace-maker, but him, a demigod who wields a Celestial Bronze sword and kills monsters, not the type that he is living with currently, but the type that hated his guts and wanted to devour his flesh? He DEFINITELY fitted in. Being almost like a normal family, shopping for supplies and groceries on Sunday and eating together at the table in the evening, the last thing he honestly expected was a monster attack. ESPECIALLY Kelli the Empousai yelling in front his face at the local supermarket,

"PERSEUS JACKSON, I AM HERE FOR REVENGE. IT WAS PAINFUL DOWN IN TARTARUS. ESPECIALLY THAT TIME WHEN YOUR GIRLFRIEND LITERALLY STABBED ME IN THE BACK. I REPEAT, I AM HERE FOR REVENGE!!!!!"

Seriously, she frightened the hell out of him, screaming so loud she was like a whiny ex-girlfriend who came back to the same boy, asked him to make up with her, be her boyfriend again, and got rejected.

Of course, the mortals couldn't see anything, due to Kelli's excellent manipulation of the mist. Sans, and Frisk, which came with him too, also didn't see or hear it, because they were too busy arguing about which shampoo was best for a goat's fur.

From:

"Sans, I think this shampoo is better suited for fur. The one you're holding is the anti-lice shampoo."

"No. The one I'm holding is better than-"

"But- "

"No 'buts'. It's going to be this shampoo!"

"Sans, I'm sorry to interrupt, but- THIS IS BETTER!!"

"WELL REALLY?? YOU LITTLE- PROVE IT!!"

To:

"YOU WOULDN'T KNOW ANYTHING BECAUSE YOU ARE A SKELETON, YOU NITWIT, I'M A HUMAN. I KNOW STUFF IN THE HUMAN WORLD!!"

"JUST BECAUSE I AM A SKELETON DOESN'T MEAN THAT I AM FOOLISH AT THIS ISSUE! DON'T UNDERESTIMATE ME, KID!!"

He hated to admit it, but seriously, this was amusing. He was enjoying himself until Kelli suddenly jumped and snatched Frisk in her claws. It was time that Sans put down the anti-lice shampoo and was actually concerned about Frisk.

"What are you doing to the kid?" Sans asked coldly, his eye sockets darkening. He summoned a Gaster Blaster, which blasted a hole through the wall, knocking bottles of shampoo over. Kelli dodged, and laughed.

"Your flimsy blasters can't do anything to me," Kelli smiled, tracing her claw down Frisk's skin, leaving a blood trail, also damaging their HP by 5.

Percy quickly pulled out Riptide, uncapped it, and held it to Kelli's throat.

"Perseus Jackson," She cackled, "pleasant to fight with you again."


	4. 4

**A/N: I'm REALLY REALLY sorry for the long wait.. I was busy with classes and homework. Now I have free time, I'm going to continue this.**

 **Disclaimer: I don't own either Undertale or PJO.**

"What are you? And how do you know his name?" Sans snarled, summoning bones to attack the empousa, one of them passing right through her right leg, not doing any harm.

"W-what? Why didn't it do anything?" Sans muttered, glaring at Kelli.

Kelli laughed, her throat close to being slit by Riptide, "Your petty bones cannot harm me, skeleton."

Percy lowered his sword and looked up at Kelli, his expression calm and unreadable. "Kelli. What are you doing here?"

"To kill you, of course, son of Poseidon." Kelli spoke, looking at him innocently. Percy swung Riptide at her again, but Kelli dodged, like a martial arts master with experience. She then swung her claws at him, trying to hurt him. Percy managed to duck, only earning a small scratch on his cheek.

"Give up, Perseus Jackson." Kelli smiled, the corners of her mouth stretching to inhuman amounts. But then the smile disappeared as Percy sliced his sword through Kelli's neck and her chalk white face scrunched up in pain. Her body disappeared, and instead of her presence, a pile of golden dust was sitting on the concrete floor. Frisk's eyes widened, holding on to Sans as they shivered, a chill running down their spine. Percy turned back to them, his sword raised. Sans' eye flared blue as he stepped in front of Frisk.

"Don't hurt the kid."

Percy raised his eyebrow, looking at Sans weirdly. "And why would I do that?" Riptide shrank into a normal ballpoint pen as Percy put the cap on.

"And what's with all the 'Son of Poseidon' crap?" Sans growled, his face full of suspicion.

"It's not what you-" Percy started, to say, his eyes wide with worry, but his sentence was cut short by Sans.

"Kid," Sans narrowed his eye sockets, "you have a lot of explaining to do."

 **A/N: Btw, sorry for the crappy fight scenes.. I tried my best**..


End file.
